This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Heavy prolonged endurance exercise has been reported to impact the immune response following activity. Significant leukocytosis, monocytosis, neutrophilia, and lymphocytosis have been reported following exercise;however, during the recovery, significant lymphocytopenia has occurred. This investigation seeks to study changes in leukocyte subsets (monocytes, neutrophils, and lymphocytes) and cortisol responses, following two different settings (resistance exercise and rest). In addition, the role of peripheral blood mononuclear cells (PBMC) gene expression in response to resistance exercise will be studied using cDNA microarray technology. One major goal is to determine whether any PBMC genes are altered as a result of the resistance exercise, as compared to just observing the leukocyte count changes within the circulation. It appears that micorarray technology may reveal which genes are expressed in human peripheral blood following an acute bout of exhaustive exercise. Ten healthy males with a minimum of 2 yrs of weight training experience will engage in two different experimental conditions using a randomized-block design: resistance exercises (back squat and leg press) including 4 sets of 10 repetitions at 65% of one-repetition maximum (1-RM), and they will serve as their own controls by remaining seated for 2.5 hrs. Research is warranted to identify additional factors and mechanisms responsible for the leukocyte trafficking, and examine gene expression and potential transcriptional pathways that are associated with exertional resistance exercise. Gene expression in PBMCs following exercise may provide insight for strategies for the clinical treatment with exercise related stress or injury.